There is known a self-hardening molding apparatus that drops self-hardening foundry sand kneaded by adding a hardener and a binder into foundry sand into a molding flask so that the molding flask is filled with the self-hardening foundry sand to be hardened to form a mold without passing through a drying process.
When a relatively large mold is formed by using this kind of self-hardening molding apparatus, there is a risk that the self-hardening foundry sand does not uniformly fill throughout the pattern if the kneaded self-hardening foundry sand is simply thrown into a molding flask including the pattern. As a result, a cavity or the like may be generated to fail to accurately form a mold.
Thus, when a relatively large mold is formed by using a self-hardening molding apparatus, a veteran technician operates the molding apparatus to properly move a discharge port of foundry sand above a molding flask and level foundry sand while leveling self-hardening foundry sand to uniformly fill throughout the pattern with the self-hardening foundry sand to form a mold. For that, when a relatively large mold is formed by using this kind of self-hardening molding apparatus, a veteran technician must be needed. Thus, it is difficult to widely form molds with an enough amount of production in many companies that lack veteran technicians.
For this reason, Patent Literature 1 described below has proposed a self-hardening molding machine capable of automatic operation. This conventional self-hardening molding machine includes first and second arms for kneading and supplying self-hardening foundry sand, the first and second arms being pivotally controlled by a servo motor of a driving system. When these arms are used, a veteran technician first throws the self-hardening foundry sand into a molding flask while manually moving the arms without using the driving system. Then, pulses generated from a rotary encoder attached to each of the arms, in response to movement of each of the arms, are counted to store the number of pulses indicating a rotation angle of each of the arms in a storage device.
At the time of automatic operation, the number of pulses indicating the rotation angle of each of the arms is read out from the storage device, and then the servo motor is controlled and driven on the basis of the number of pulses to automatically rotate the first and second arms. Subsequently, the self-hardening foundry sand is thrown from a discharge port provided at a leading end of the second arm into the molding flask.